Process for the stabilization of crude oils is understood to mean the operation which consists in bringing the flowing pressure of the crude oil at the well outlet, generally of between 10 and 100 bars, to atmospheric pressure, a Reid vapor pressure of the order of 0.69 bar at 38.degree. C., determined by the API standard D323, being observed, while limiting losses to the atmosphere of light hydrocarbons, especially C.sub.3.sup.+ hydrocarbons, that is to say consisting of three to seven carbon atoms, commonly known as C.sub.3, C.sub.4, C.sub.5, C.sub.6 and C.sub.7 hydrocarbons. The aim of such a process is, of course, to maximize the production of crude oil while attempting to recover the maximum of C.sub.3.sup.+ but while obtaining a stabilized crude oil which does not degas or which only degasses very slightly.
Currently, in order to stabilize a crude oil on an oil field, a process involving a number of successive flashes is used. This is a process of decompression in a number of stages, which makes it possible to lower the pressure of the crude oil, which is mainly accompanied by not always controllable degassing of the lightest C.sub.3.sup.- hydrocarbons, that is to say hydrocarbons consisting of less than three carbon atoms, i.e. C.sub.3, C.sub.2 and C.sub.1. However, it is impossible, by successive flashes, to degas the crude oil while being limited solely to C.sub.3.sup.- hydrocarbons; inevitably, C.sub.3.sup.+ hydrocarbons are entrained in the gases which are not recovered and C.sub.3.sup.- hydrocarbons remain diluted in the crude oil. This process by flashes does not make it possible to selectively separate C.sub.3.sup.- hydrocarbons from the crude oil without degassing other products with a higher added value. The presence of C.sub.3.sup.- in the stabilized crude oil makes it more sensitive to temperature and pressure variations during subsequent operations, since the C.sub.3.sup.- can degas inopportunely.
This problem of the subsequent degassing of crude oil, especially during its storage or its transportation, either by boat or by pipeline, can be the source of many difficulties and especially of possible accidents.